Measurement of CP Asymmetries and Branching Fractions in B -> pi pi and B -> K pi decays

TL;DR

This paper reports measurements of CP asymmetries and branching fractions in B meson decays to pi pi and K pi, providing insights into CP violation and CKM angle alpha with data from the BABAR detector.

Contribution

First measurements of CP asymmetries and branching fractions in B -> pi pi and K pi decays using 347 million BBbar events, constraining the CKM angle alpha.

Findings

CP violation in B0 -> pi+ pi- is excluded at 3.6 sigma.

Measured CP asymmetries and branching fractions align with Standard Model predictions.

Bounds on the CKM angle alpha are derived from the results.

Abstract

We present preliminary measurements of the CP asymmetries and branching fractions for B -> pi pi and B -> K pi decays. A total of 347 million BBbar events collected by the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC are used for these results. We find Spipi = -0.53 +- 0.14 +-0.02, Cpipi = -0.16 +- 0.11 +- 0.03, AKpi = -0.108 +- 0.024 +- 0.008, BF(B0 -> pi0 pi0) = (1.48 +- 0.26 +- 0.12) x 10^-6, BF(B+ -> pi+pi0) = (5.12 +- 0.47 +- 0.29) x 10^-6, BF(B+ -> K+pi0) = (13.3 +- 0.56 +- 0.64) x 10^-6, Cpi0pi0 = -0.33 +- 0.36 +- 0.08, Apipi0 = -0.019 +- 0.088 +- 0.014, AKpi0 = 0.016 +- 0.041 +- 0.012. The measured values of Spipi and Cpipi imply that CP conservation in B0 -> pi+ pi- decays is excluded at the 3.6 sigma level. From these results we present bounds on the CKM angle alpha.